Grinding Tools that Contain Uniform Distribution of Abrasive Grits and Method of Manufacture Thereof

ABSTRACT

The present invention relates to a method of uniformly distributing abrasive grits on grinding tools. It can be applied in the cutting, grinding segments of diamond tools, which are typically used in cutting and drilling various hard and fragile materials, such as granite, marble, concrete, asphalt, etc. The present invention provides a template, the template designed based on the arranging requirement of abrasive particles such as diamond grits. The template can adsorb only a single layer of abrasive particles and is then placed onto a sheet, where the diamond grits are pressed into the sheet, with the diamond grits distributed uniformly on the sheet.

RELATED APPLICATIONS

This is a continuation of International Application PCT/CN2008/000331,with an international filing date of Feb. 13, 2008.

FIELD OF THE INVENTION

The present invention relates to the cutting and grinding tools, such asthe cutting segments of diamond tools, which are typically used incutting and drilling various hard and fragile materials, such asgranite, marble, concrete, asphalt, etc. More particularly, the presentinvention relates to the uniform distribution of abrasive particles suchas diamond grits on the segments of cutting tools to increasing thecutting efficiency.

BACKGROUND OF THE INVENTION

Synthetic diamonds are the hardest abrasive material currently known,and they have been widely used as super-abrasives on cutting andgrinding tools. Diamond tools are particularly used to cut and grindrocks in machining stone and other structural components. Diamond toolsmainly have cutting segments on which diamonds or other abrasiveparticles are distributed. The cutting segments are fixed on the toolbodies.

A satisfactory structure of diamond saw blades is where the diamondparticles have a relatively large exposed portion and proper spacing ofparticles to improve the excluding of debris and the transporting ofcooling fluid, thus improving the cutting efficiency and lengthening theuseful life of the tools. Uniform distribution of abrasive grits canalso improve safety in their manufacture. A typical abrasive tool, suchas a diamond saw blade, is manufactured by mixing diamond particles(e.g. 40/50 U.S. mesh) with a suitable support matrix (bond) powder(e.g. cobalt powder of 1.5 micrometer in size). The mixture is thencompressed in a mold to form the desired shape. This “green” form of thetool is then consolidated by sintering at a temperature between700-1200° C. to form a single body with a plurality of abrasiveparticles therein. Finally, the consolidated body is brazed to a toolbody, such as the round blade of a saw, to form a cutting tool.

Different applications, however, require different combinations ofdiamond and support matrix. For example, drilling and sawingapplications may require a larger-sized (20 to 60 U.S. mesh) diamondgrit to be mixed with a metal powder. The metal powder is typicallyselected from cobalt, nickel, iron, copper, bronze, or alloys thereof,and/or mixtures thereof. For grinding applications, a smaller-sized(60/400 U.S. mesh) diamond grit is mixed with either metal (typicallybronze), ceramic/glass (typically a mixture of oxides of sodium,potassium, silicon, and aluminum) or resin.

Because diamonds are much larger than the matrix powder, and is muchlighter, it is very difficult to mix the two to achieve uniformity.Moreover, diamond particles can still segregate from metal powder in thesubsequent treatment, such as when pouring the mixture into a mold, orwhen the mixture is subjected to vibration.

One method used in an attempt to make the diamond distribution uniformis to wrap diamond particles with a coating of matrix powder. Theconcentration of diamond particles in each diamond tool is tailored fora particular application. The concentration determines the averagedistance between diamond particles. If one thickly coated diamond mixesthe coated particles together, the distribution of diamond would becontrolled by the thickness of coating and may become uniform.Additional metal powder may be added as an interstitial filler betweenthese coated particles to increase the packing efficiency so that theconsolidation of the matrix powder in subsequent sintering would beeasier.

Although the above-described coating method has certain merit, inpractice, uniformity of coating is very difficult to achieve. Forexample, Chen and Sung (U.S. Pat. Nos. 5,024,680 and 5,062,865) describea chemical vapor deposition (CVD) method for coating diamond grit usinga fluidized bed. However, most of these methods can only produce thincoatings such as a few micrometers thick that do not affect the diamonddistribution. Moreover, chemical coating methods typically requiretreatment at high temperatures such as greater than 900° C. that maycause damage to the diamond. It is well known that synthetic diamondgrit tends to form micro-cracks above this temperature.

Dr. Song Jian Min of Taiwan has invented a two-dimensional method,firstly providing a layer of support matrix, and disposing abrasivegrits in the support matrix layer in a desired pattern. After thediamond particles are plated into the metal matrix layer according to apredetermined pattern, the process may be repeated until a desirednumber of layers have been formed. The layers are then assembled to formthe desired three-dimensional body. Subsequently the diamond tool isconsolidated to form the final product.

The detailed above-mentioned method is as follows: forming a thin layerof bonding matrix (i.e. a two-dimensional body); placing a template onthe bonding matrix, with the template having a plurality of aperturesformed therein which are sized to receive a abrasive grit of aparticular size, with one particle being disposed in each aperture; and,as the particles are filled into the apertures, they are subjected topressure or moved into the bonding matrix. However, as the abrasiveparticles are small to 40/50 U.S. mesh, it is imposable to fill theapertures with abrasive particles one by one, and so this method cannotachieve industrialization.

In summary, current methods are incapable of controlling the uniformityof diamond particles in cutting tools efficiently. Likewise, the currentmethods are inadequate to provide effective control of size variationsand concentration variations of different parts of the same tool.

SUMMARY OF THE INVENTION

Performance of diamond arranged in a predetermined pattern /uniformdistribution:

The distance between diamond or other abrasive particles determines thework load each particle will perform. Improper spacing of the abrasiveparticles will lead to premature failure of the abrasive surface orstructure. If the abrasive particles are too close to one another, someof the particles are redundant and add to the cost. Moreover, thesenon-performing particles can block the passage of debris, therebyreducing cutting efficiency.

If the diamond grits are uniformly distributed, the distance between thegrits will be optimized according to the cutting materials and cuttingconditions. It has be found that in practice, 85% of the distancesbetween diamond grits on uniform distributed saw blade are 2 mm-5 mm,while on traditional saw blades, this percentage is only 60%. Theincreasing of diamond content weakly affects the work load, but theapplicable cutting times are lengthened markedly, thus the cuttingefficiency is increased and useful time of the saw blade is lengthened.

Diamond concentration: when the concentration of diamond increased, theuseful time of uniform distributed diamond will be lengthened ingeometric series, and maintaining favorable cutting and sawingcapability at the same time, but when the concentration increased more,the cutting and sawing capability will be reduced.

The exposed height of diamond particularly affects the sawing efficiencyand the useful time of the saw blade, it is rest with the size and thedistribution of diamond and the hold of the sheet. So, the uniformdistribution of diamond or other abrasive particles on matrix willmarkedly affect the cutting and grinding tools. The object of thepresent invention is to provide a method of arranging the abrasiveparticles uniformly on cutting and grinding tools, and the method can beindustrialized.

One art of the present invention is to provide a sheet;

A template, designed on the single-layer arranging requirement ofdiamond or the other abrasive particles, said template has a layer ofadsorbent which can adsorb a single layer of diamond grits.

Place the template on the sheet, press the diamond grits into the sheet,the diamond grits will be imbed uniformly on the sheet at a layer.

Said template comprising adsorbent, wherein the adsorbent has a lowerviscosity, a higher percent of condensate and a lower percent ofsolvent.

Said sheet is a paste, after the diamond pressed into it, the pastewould be solidified by means of heating or cooling to be a sheet with asingle layer of uniformly-distributed diamond grits.

Said sheet is made of the mixing of metal power and bond, when themixing is about to solidified, press the abrasive particles into onesurface or double-surface of the sheet.

Press a plurality of above-mentioned sheets to be a one on the thicknessrequirement of cutting tool, then placed them into a mold to besintered.

Said cutting tool including multiple sheets, the distribution pattern ofabrasive particles on each layer are the same as or different; forexample, the outer layer has a higher density of diamond while the innerlayer has a lower density and bigger-size diamond.

Another art of the present invention is as follows:

A sheet;

An electric/electromagnetic template, designed on the arrangingrequirement of diamond or the other abrasive particles,

Diamond or the other abrasive particles are adsorbed on the template ina layer;

Press the template with the adsorbed diamond into the sheet, thenseparate the template, the diamond grits will be uniformly distributedon the sheet;

Said template is a plane template formed by the following steps: afterelectromagnetic radiating, covering the positions where does not need toadsorb abrasive particles, thus an electromagnetic template is formed.

Said template can be a plasma-template.

Said template can be an electric template with positive or negativecharge.

Said sheet is made by the mixing of metal power and bond compressed in amold.

Select needed layers of sheets on the requirement of cutting, compressthe multiple sheets above-mentioned to be a one by static press orstamping press, then placed them into a mold to be sintered.

Said cutting tool is formed by multiple sheets, the distribution patternof abrasive particles on each layer are the same as or different; forexample, the outer layer has a higher density of diamond while the innerlayer has a lower density and bigger-size diamond.

Therefore, the present invention provides a template, the shape and thepattern of the template can be designed conveniently on the arrangingrequirement of abrasive particles, and the template can adsorb onlysingle layer of abrasive particles, place the template with uniformlydistributed abrasive particles into or adhere to sheet, then will form asheet with uniformly distributed abrasive particles, thus the positionof abrasive particles can be located exactly on the sheet onpredetermination. The abrasive particles can be uniformly distributed,or arranged on the requirement of accounted cutting force of providedcutting and grinding tools, For example, higher concentration diamondgrits are preferred in the edge and front of saw, while in the middle,the lower concentration diamond grits are preferred.

In practice, compared with irregularly distributed diamond saw blade,the saw blade with uniformly distributed diamond grits has a lowerconcentration diamond grits, the practical cutting distance is 1150 m(the distance of irregularly distributed diamond saw blade is 450 m),the blade cuts smoothly and there is not collapse piece of blade, thesum power consumption of abrasive tools decrease 30 percents, the noiseof perigee decrease 10 db(A), cutting efficiency increase 30 percents,and the useful life is three times longer than those irregularlydistributed diamond saw blade.

The foregoing was intended as a broad summary only and of only some ofthe aspects of the invention. It was not intended to define the limitsor requirements of the invention. Other aspects of the invention will beappreciated by reference to the detailed description of the preferredembodiment and to the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described by reference to the detailed descriptionof the preferred embodiment and to the drawings thereof in which:

FIG. 1 shows the uniform distribution of abrasive particles formed bythree sheets.

FIGS. 2A, 2B, and 2C are views of the template structure, wherein FIG.2A shows the oblique distribution of abrasive particles, FIG. 2B showsthe forward distribution of abrasive particles, and FIG. 2C shows thecross distribution of abrasive particles.

FIG. 3 shows the diamond grits adsorbed on the electromagnetic template;and

FIG. 4 shows another layout of a segment of a cutting tool formed bymultiple sheets of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a perspective view of a segment of diamond tool, indicatedat 10. The segment 10 is formed by a plurality of layers, 11, 12, 13,and 14, which are impregnated with abrasive grits, indicated ashexagonal frame 1.

Referring to FIGS. 2A, 2B, and 2C, electromagnetic template 20 of thepresent invention is capable of adsorbing single layer of abrasiveparticles (for example, diamond grits) after the corona is discharged.When the adsorptive points are occupied by the adsorbed diamond grits,the other grits can not be adsorbed on the same place, so the adsorbedgrits form a single layer, and the template can be designed on therequirement of the arrangement of diamond or other abrasive particles.Thus the diamond, cubic boron nitride grits are uniformly distributed onthe template, and the distribution form can be designed freely on thedesire of the designers.

FIGS. 2A, 2B, and 2C are views of the distribution of abrasive particleson the template, wherein FIG. 2A shows the oblique distribution ofabrasive particles, FIG. 2B shows the forward distribution of abrasiveparticles, and FIG. 2C shows the cross distribution of abrasiveparticles.

In practice, the template may be a plane (as shown in FIG. 3). Inaddition, a cover 21 may be adhered on the template, which covers thepositions that do not need to adsorb abrasive particles, when theabrasive particles such as diamond grits adsorbed on template, thenachieve uniform distribution of diamond grits on the template. Theadvantage of this method is that the template is easily treated with,and the shape of the cover is freely and easy treated.

Referring to sheet 30, there are many ways to make the sheet. Forexample, the powder can first be mixed with a suitable binder (typicallyorganic) and a solvent that can dissolve the binder. In order to preventthe powder from agglomerating during the processing, a suitable wettingagent (e.g., phosphate ester) may also be added. The slurry can then bepoured onto a tape and pulled underneath a blade or leveling device,allowing the sheet to be made. The tape casting method is a well-knownmethod in rubber and plastic manufacturing. By adjusting the gap betweenthe blade and the tape, the slurry can be cast into a sheet with theright thickness.

It is desirable to make the sheets pliable for subsequent treatments(e.g., bending over the tool substrate, which has a curvature).Therefore, a suitable organic plasticizer can also be added to providethe desired characteristics. The use of organic agents for powderprocessing is documented in many textbooks and it is well known by thoseskilled in the art. Typical binders include polyvinyl alcohol (PVA),polyvinyl butyral (PVB), polyethylene glycol (PEG), paraffin, phenolicresin, and acrylic resins. Typical binder solvents include methanol,ethanol, acetone, trichloroethylene, toluene, etc. Typical plasticizersare polyethylene glycol, diethyl oxalate, triethylene glycoldihydroabietate, glycerin, rosin, etc. The organic agents so introducedare to facilitate the fabrication of metal layers. They must be removedbefore the consolidation of metal powders. The binder removal process isalso well known to those skilled in the art.

Once the sheet 30 is formed, a template impregnated with diamonds orother abrasive particles is laid on the top of the sheet. After thetemplate is properly positioned, the abrasive particles are pressed intothe sheet, and the template is removed. The abrasive particles are nowuniformly distributed on the sheet. The depth of the abrasive particlesembedded in the sheet can be varied based on specific requirements, andthose skilled in the art will know the desirable height of the abrasiveparticles to extend outwardly from the sheet.

The manufacture of the template may be as follows: after electromagneticradiating on a metal template, the template will be with adsorbability,then place a cover (e.g. a cardboard) on the template, covering thepositions where does not need to adsorb abrasive particles, thus thetemplate can achieve uniform distribution of abrasive particles.

The template may also be a plasma template, having well single layeradsorbability.

The template may also be an electric template, having adsorbability witha negative charge.

FIG. 4 shows the sheets of the present invention with uniformdistributed abrasive particles assembled transversely. The segment inFIG. 4 is formed from a plurality of transverse sheets 41. Thedifference of it is that because the segment is formed transversely, itrequires that the abrasive particles be distributed transversely on thetool, and the template manufactured based on that requirement. Insummary, the location methods of abrasive particles are various, andthey can all conveniently achieve the uniform distribution of abrasiveparticles according to the present invention.

ALTERNATE EMBODIMENTS

This is the same as the preferred embodiment, except that the templateis with bond, whose adsorbability is by chemical material rather than byelectromagnetic adsorbability as in the preferred embodiment.In a further embodiment, 40/50 U.S. mesh diamond grit (SDA-85, made byDE BEERS company) was used. The sheet was a mixture of metal powder andacrylic resin. Five different proportions of cobalt and bronze were usedfor the metal powder. An acrylic binder was added to the mixture and thecharge was blended to form a cake. The cake was then rolled between tworollers to form sheets with a thickness of 1 mm. Then, the templatedistributed with adsorbed diamond grits was placed on the sheet, and thediamond grit was pressed into the sheet. The template was then removed.The sheets were cut in the shape of diamond saw segments with a lengthof 40 mm and width of 15 mm. Three each of such segments were assembledand placed into a typical graphite mold for making conventional diamondsaw segments. The segments were pressed and heated by passing electriccurrent through the graphite mold. After sintering for three minutes,the segments were consolidated to a height of 9 mm with less then 1%porosity. Twenty-four segments for each composition were fabricated, andthey were laser-welded onto a circular saw of 14 inches in diameter. Theperformance of these blades was better than those made by conventionalmethods in sawing the granite.

The present invention provides an adsorptive template where the shapeand the pattern of the template can be designed conveniently based onthe specific arranging requirement of the abrasive particles. Thetemplate can adsorb only a single layer of abrasive particles. place thetemplate with uniformly distributed abrasive particles into or adhere tosheet, then will form a sheet with uniformly distributed abrasiveparticles, thus the position of abrasive particles can be locatedexactly on the sheet with determination. The abrasive particles can beuniformly distributed, or arranged based on the requirement of accountedcutting force of provided cutting and grinding tools. For example,higher concentration diamond grits are preferred in the edge and frontof the saw, while in the middle, lower concentration diamond grits arepreferred.

It will be appreciated by those skilled in the art that the preferredembodiment has been described in some detail but that certainmodifications may be practiced without departing from the principles ofthe invention.

1. A method of uniformly distributing abrasive grits on grinding orcutting tools, comprising the steps of: providing a template designed onthe single-layer arranging requirement of diamonds or other abrasiveparticles, said template having a layer of adsorbent material capable ofadsorbing a single layer of diamond grits; placing said template on asheet, pressing said layer of diamond grits into said sheet, saiddiamond grits being embedded uniformly on said sheet in a layer.
 2. Themethod of claim 1, wherein said adsorbent layer has a lower viscosity, ahigher percent of condensate and a lower percent of solvent.
 3. Themethod of claim 1, wherein said sheet is a paste, wherein said pasted issolidified, after said diamond grits are pressed into said paste, bymeans of heating or cooling to form a single layer ofuniformly-distributed diamond grits.
 4. The method of claim 1, whereinsaid sheet is made by mixing metal powder and bond to form a mixture,and wherein when said mixture is about to solidify, said abrasiveparticles are pressed into either one surface or both surfaces of saidsheet.
 5. The method of claim 1, further comprising the steps of:pressing a plurality of said sheets to form a composite with a thicknessas required by said grinding or cutting tools; placing said compositeinto a mold to be sintered.
 6. The method of claim 1, wherein saidgrinding or cutting tools comprises multiple sheets and wherein thedistribution pattern of abrasive particles on each layer are the same asor different.
 7. The method of claim 1, wherein the outer layer of saidgrinding or cutting tool has a higher density of diamond grits and theinner layer has a lower density and bigger-size diamond grits.
 8. Themethod of either claims 1 or 5, further comprising the following steps:cutting said sheets into diamond saw segments in a predetermined shape,assembling a plurality of such segments and placing said segments into agraphite mold for forming conventional diamond saw segments; sinteringand consolidating said segments; and laser welding said segments onto acircular saw.
 9. A method of uniformly distributing abrasive grits ongrinding tools comprising the steps of: providing a sheet; providing anelectric/electromagnetic template, designed based on the arrangementrequirement of diamonds or other abrasive particles; adsorbing saiddiamonds or other abrasive particles on a template in a layer; pressingsaid template with the adsorbed diamonds or other abrasive particlesonto said sheet; separating said template from said sheet, wherein saiddiamonds or other abravise particles will be uniformly distributed onthe sheet.
 10. The method of claim 9, wherein said template is a planetemplate formed by electromagnetic radiating and covering the positionswhere it is not needed to adsorb abrasive particles.
 11. The method ofclaim 9, wherein said template is a plasma-template.
 12. The method ofclaim 9, wherein said template is an electric template with a positiveor negative charge.
 13. The method of claim 9, wherein said sheet ismade by mixing metal powder and bond compressed in a mold.
 14. Themethod of claim 9, wherein said sheets of selected layers on therequirement of cutting were compressed to be a one by static press orstamping press, then placed into a mold to be sintered.
 15. The methodof either claims 9 or 14, wherein the cutting tool is formed by multiplesheets, the distribution pattern of abrasive particles on each layer arethe same as or different.
 16. The method of claim 15, wherein the outerlayer has a higher density of diamond while the inner layer has a lowerdensity and bigger-size diamond.
 17. The method of claim 9, furthercomprising the steps of cutting the sheets impregnated withuniform-distributed diamond grits into diamond saw segments; assemblinga plurality of segments; placing said segments into a graphite mold formaking conventional diamond saw segments; sintering and consolidatingsaid segments, the segments were consolidated; and. laser welding saidsegments onto a circular saw.